Effects Of Different Internal Fixation On Fractures Healing And Changes On Morphology

Objective: To observe the effects of internal fixation on the process of fractures healing in rabbit and the changes on morphology and to explore the difference among the different internal fixation. Methods: Twenty seven New Zealand white rabbit were randomly divided into 3 groups and 9 rabbit in each group to build the animal model of fractures in the middle part of thighbone. They were fractures in the middle part of thighbone with periosteum by plate internal fixation (Group I), fractures in the middle part of thighbone peeling off periosteum and accompanied with plate internal fixation (Group II) and fractures in the middle part of thighbone with periosteum but getting out medulla and fixed with intramedullary nail (Group III), respectively. X-ray film was shot in each group at different time points. In order to observe the fracture healing, the rabbits were sacrificed in different groups at the same time point. The callus was measured at the location of fracture healing. Then it was sampled for continuous slide with HE stain to observe the morphologic changes of fracture healing under microscope. Results: 1)The x-ray film indicated at the same time point amount of callus was formed in group III but less in group I and II. 2)Under the microscope: the periosteum was thickened obviously in group III. The cartilage cells were abundant and distributed widely. The order was from poorly differentiated to well ones by turns with outside to inside. The bone trabeculae were commonly accompanied with the presence of bony matrix. The degree of periosteum thickening and the amount of cartilage cells in group I and II were less than in group III. The bone trabeculae were with cartilage matrix. 3)On diameter of callus: the difference on diameter of callus between group I and group II wasn't significant (P>0.05). The differences between group I and III, group II and III were significant (P<0.05). Conclusion: 1)The group with internal fixation by intramedullary nail was excelled than those with plate internal fixation. During the process of fracture healing, the reaction of proliferation was distinct and the callus was plenty, which helps to the identification of fracture healing, the calcification of callus and early functional practice or with weight loading. 2)The peeling of part periosteum did not affect the healing of fracture, neither did endosteum.